Root file system NOT resized on first boot

I've burned the latest image available for ODROID C2 (ODROID C2 OMV image) onto a micro-SD card using Etcher. According to the readme it's supposed to automatically resize the root partition on first boot, but it doesn't. I've actually tried it twice (re-burned the image onto the card), I've waited for hours after the first boot, but it just doesn't properly resize the root partition.

I have a 64GB micro-SD card, but when I execute "df -h" I see this:

Source Code

root@odroidc2:~# df -h

Filesystem Size Used Avail Use% Mounted on

/dev/mmcblk0p1 7.3G 1.5G 5.8G 20% /

udev 10M 0 10M 0% /dev

tmpfs 344M 11M 334M 3% /run

tmpfs 860M 0 860M 0% /dev/shm

tmpfs 5.0M 8.0K 5.0M 1% /run/lock

tmpfs 860M 0 860M 0% /sys/fs/cgroup

tmpfs 860M 16K 860M 1% /tmp

folder2ram 860M 3.7M 856M 1% /var/log

folder2ram 860M 0 860M 0% /var/tmp

folder2ram 860M 0 860M 0% /var/lib/openmediavault/rrd

folder2ram 860M 792K 859M 1% /var/spool

folder2ram 860M 11M 849M 2% /var/lib/rrdcached

folder2ram 860M 8.0K 860M 1% /var/lib/monit

folder2ram 860M 4.0K 860M 1% /var/lib/php5

folder2ram 860M 4.0K 860M 1% /var/lib/netatalk/CNID

folder2ram 860M 460K 859M 1% /var/cache/samba

tmpfs 172M 0 172M 0% /run/user/0

Display All

As you can see, the total size is far from 64 GB and the root partition (/dev/mmcblk0p1) is only 7.3G in size.

How can I resize the root partition manually to use the remaining free space on the card?